Efficacy of cleaning and sanitizing procedures to reduce Listeria monocytogenes on food contact surfaces commonly found in fresh produce operations

Abstract

Cleaning and/or sanitizing methods were evaluated to reduce Listeria monocytogenes (Lm) on coupons of porous (PS; polyester-nylon with coating conveyor belt [PNCB], plywood [PW]) and non-porous (NPS; high density polyethylene, stainless steel) surfaces. Coupons (2.5 cm diameter) were inoculated with six-strain cocktail with cabbage juice, inverted and incubated on tryptic soy agar with yeast extract (TSAYE; 37 °C, 24 h). Coupons (n = 4; ∼9 log CFU/coupon) were rinsed only (RO), multi-step cleaned (MSC), sanitized only (SO; peroxyacetic acid [PAA], bleach, quaternary ammonium compounds [QAC]), or cleaned and sanitized (MSC + S), transferred to Dey/Engley broth (DEB) with glass beads (1 g), vortexed and enumerated on Harlequin-TSAYE. Half of the coupons were dried prior to transfer to DEB. MSC resulted in ave. 2 log CFU/coupon reductions on NPS, and 0.6–1.1 log on PS. MSC + S led to >5-log reduction on NPS (81%; n = 48). On PS, MSC + S-PAA resulted in 1.8 and 1.9 log reductions on PW and PNCB, respectively. RO and SO reduced Lm on all surfaces, although less effectively than MSC and MSC + S. On PS, MSC + S-PAA was most effective, followed by bleach and QAC (p < 0.05). Drying after sanitizing increased Lm reduction by ∼0.4 log (p < 0.05). Partial cleaning and/or sanitizing leads to minimal reduction of Lm, while multi-step cleaning with sanitizing is highly effective.